1. Field
The present invention relates to a computer controlled electric syringe for injecting a medicinal solution to be used in medical treatment or dental treatment.
2. Description of the Related Art
As an instrument which injects a medicinal solution such as an anesthetic, for medical treatment or dental treatment, a manually operated syringe is generally used. In order to alleviate pain using this syringe, it is difficult to perform injection at a low speed and a constant injection speed. Additionally, when a medicinal solution is injected into a hard tissue, large pressing is required, and an operator is forced to make an effort. Moreover, in this case, since the injection speed is sharply changed with fluctuation of the pressing during injection, this can be also a factor which causes pain.
Thus, an electric syringe for injecting a medicinal solution, which is capable of performing injection at a slow injection speed, and also capable of performing injection into a hard tissue while maintaining a constant injection speed is now being widely used.
A conventional configuration that relates to such an electric syringe is disclosed in JP-A-2004-130005 (counterpart U.S. publication is: US 2004/0073168 A1). The publication, JP-A-2004-130005, discloses an electric syringe which is classified into a gun type from its shape, and an electric syringe for a dental treatment anesthetic in which a piston presses and moves a rubber plug of a cartridge in which an anesthetic is enclosed, thereby making the anesthetic flow into a dental injection needle, and makes the anesthetic discharged from a needle tip. In this electric syringe for a dental treatment anesthetic, the injection speed is increased at the beginning of injection, and a constant injection speed is obtained after the lapse of a predetermined period so that pain is kept from occurring.
Another conventional configuration, which is related to the computer controlled electric syringe, is disclosed in JP-T-2004-516107 (counterpart international publication is: WO 02/051476 A1). In JP-T-2004-516107, an electric syringe which is classified into a pen type from its shape is disclosed, and generation of a pain is suppressed because driving is made by the control of an electronic control unit.
The electric syringe for injecting a medicinal solution requires the improvement in usability by realization of a cordless type and miniaturization. Additionally, various questionnaire researches have shown that the pen type which is smaller than the comparatively large-sized gun type has good and preferable usability.
In the electric syringe for a dental treatment anesthetic described in JP-A-2004-130005, although a high torque and a low-speed rotation are realized using a speed-reducing mechanism by a plurality of two-stage gears, there is a problem in that there is no room in internal structure, and additional miniaturization is not easy. A driving unit capable of realizing further miniaturization is desired.
Additionally, even in the pen type injector described in JP-T-2004-516107, a high torque and a low-speed rotation are realized using a speed-reducing mechanism by a plurality of two-stage gears. However, there is a problem in that a plunger is supported at one supporting portion, and a force is concentrated on this supporting portion where damage easily occurs. A driving unit with a mechanically robust construction is desired.